UAPSD/WMM Power Save mode (T-Mobile Hotspot@Home)

Last month US carrier T-Mobile introduced their @Home product. With it a compatible T-Mobile cellphone can connect to T-Mobile’s cellular network via any T-Mobile or open WiFi hotspot. Thus homes and business with poor coverage can, in effect, set up their own cell base-station. There are also some nice service plan benefits (for +$10 unlimited free calling while connected via WiFi, etc.)

Why I’m posting here is that one of the routers T-Mobile offers as part of this program is a WRT54G-TM (for $50 w/ $50 rebate). It appears to be similar to the WRT54GL with a slightly different chipset and some custom coding. Nobody has been able to reflash it so far, and it does have a trick unavailable (yet!) elsewhere.

There is a power-saving mode not (yet!) widely supported, UAPSD which is part of WMM™ Power Save, described as “the same amount of data can be transmitted in a shorter time while allowing the Wi-Fi device to remain longer in a low-power ”dozing“ state.” (Far better explanation, & the spec).

I’m posting in the hope that this feature could get added to my much appreciated Tomato firmware. I’ve seen other parts of the same set of specifications so I suspect folks are already aware of it. Indeed I believe Windows Mobile 6 also takes advantage of this so there is an expanding set of clients.

I my case my trusty WRT54GS running Tomato “outshines” the new WRT54TM, leading to my cellphone preferentially connecting to Tomato and thus running it’s battery down faster then need be.

The phone technology is Unlicensed Mobile Access (UMA) (though in telecom it’s now referred to as Generic Access Network (GAN)) which is an IEEE standard. For an overview take a look at this Wikipedia article.

The powersaving part, on the router, is Unscheduled Automatic Power Save Delivery (UAPSD), also an IEEE standard, a sub-part of the 802.11 family (thus the link to the spec I posted above.) It is intended for any low-power device, typically a mobile device. Thus it is used in laptops, tablets, palmtops, portable media players, cameras, and phones.

UAPSD is what I’m asking be implemented in Tomato. Parts of it’s larger spec are already in Tomato, the multimedia portion, just the power-saving part doesn’t appear to be in place yet.

T-Mobile is the first with a nationwide rollout of GAN/UMA in the US, largely because they don’t have a competing landline business. However GAN/UMA is already popular in other parts of the world and other US carriers are trying it out in local and pilot programs (T-Mobile initially rolled this out in Seattle a year ago, only going national last month.)

If you’re asking about UAPSD, the router-based powersaving technology, also yes. Again, it is a router technology for any low-power client device: Laptops, tablets, palmtops, portable media players, cameras, phones, whatever. I’m interested in it for my phone; folks with PocketPCs, WiFi cameras, some laptops & tablets, etc. can also take advantage of it.

Unscheduled Automatic Power Save Delivery (UAPSD) is intended for routers supporting low-power mobile devices. Some laptops already support it (I believe a number from Dell do), as well as mobile & media devices from Samsung, Nokia, and others, as well as it being built into Windows Mobile 6.

It’s part of the multimedia extensions to 802.11. Tomato already partially implements these, I just asking/suggesting UAPSD also be implemented along with the other parts already in place.